Micrometers are conventional devices for measuring the exact distance between two objects. In some instances, such as in adjusting structural elements to the vertical, it is common practice to suspend a plumb-bob and to measure the distance between the wire of the plumb-bob and the structural element. However, it is difficult to detect exactly when the micrometer head contacts the wire, so that there is always a slight over-shoot and this renders the measurements inaccurate.